Brochs are massive, circular, prehistoric fortified dwellings some 2,500 years old. They have been built using a drystane construction method with walls typically 12 feet thick and an inside floor space of around 30 feet in diameter.

These round-houses were built and occupied from around 800BC until the second century AD. This is the earlier part of the Scottish Iron Age when defensive hill forts were being constructed in prominent and strategic positions in the landscape across the British Isles.

Dun Grugaig Broch stands on the north bank of the Abhainn a’Ghlaine Bhig, in the upper reaches of Gleann Beag. It is in the same valley as the two Glenelg brochs of Dun Telve and Dun Troddan. Unlike those two brochs which are in the valley close to flat ground, Dun Grugaig is situated on rugged rising ground. It should not be confused with the broch known as Caisteal Grugaig a few miles to the north.

Dun Grugaig is a D-shaped fortification (dun) of a type commonly regarded as a prototype broch or "semi-broch".It was built with the straight side of the fort facing the edge of the precipice on the east. It has the hollow-wall construction which is characteristic of later brochs.

The partly lintelled southeast doorway appears to be the main entrance into the building; there is a second entrance at the west end of the wall. The interior is full of rubble. Three doorways can be seen in the inner wall face. Traces of an upper intra-mural gallery can be seen on the high wall head on the south side.

Dun Grugaig has not been excavated. The earliest record of the broch seems to be by Alexander Gordon in 1720 who refers to a 'Castle Chonil' in the east part of the glen and as being distinct from the other two brochs.

This broch is by far the least known of all the broch's and because if features on so few maps, or indeed websites or in books, discovering this ancient fortification was a personal sense of achievement for me, as I'm sure would be for any castle-finder exploring some of the most fascinating, wild and remote corners of the British Isles.

Continue along the road from the more famous and impressive Broch's of Dun Telve and Dun Troddan, past Balvraid as you'll see on your map, as it winds its way upwards further into even more isolated highlands, and the road deteriorates to a rough track that unless you have a robust four-by-four, at this point you'll want to park up and continue your journey on foot. Parking is easy as you will certainly be the only vehicle for miles around, but just in case, park to one side of the track. As you walk further long the track, you'll see the river continues to your right, as the track begins to rise towards the summit of the surrounding hills. At this point the track starts to veer to the right out of sight, and it is then you will see the broch hidden and sheltered beneath the tree line. A great sense of discovery you'll feel the walk worthwhile as you leave the track and head towards this tumbled-down ancient ruin to explore its walls, taking in the fabulous views back down the glen.